From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
David Woodhouse <dwmw@amazon.co.uk>,
KarimAllah Ahmed <karahmed@amazon.de>
Subject: Re: [PATCH] KVM: VMX: expose the host's ARCH_CAPABILITIES MSR to userspace
Date: Wed, 7 Mar 2018 16:39:42 +0100 [thread overview]
Message-ID: <20180307153942.GC12290@flask> (raw)
In-Reply-To: <37a89c09-e933-9256-1b7a-3a9df846a672@redhat.com>
2018-03-07 16:10+0100, Paolo Bonzini:
> On 07/03/2018 15:56, Radim Krčmář wrote:
> > The MSR_F10H_DECFG default is questionable -- MSR_F10H_DECFG is an
> > architectural MSR, so we'd be changing the guest under the sight of
> > existing userspaces.
> > A potential security risk if they migrate the guest to a CPU that
> > doesn't serialize LFENCE. ARCH_CAPABILITIES are at least hidden by a
> > new CPUID bit.
>
> Good point. Perhaps we should add a KVM-specific CPUID bit for
> serializing LFENCE.
I reckon it wouldn't help much in the wild: we'd need userspace changes
(at least for QEMU) and at that point, userspace can as well just
implement MSR_F10H_DECFG and use an unmodified guest.
We can't easily intercept LFENCE to emulate the feature either, so it
seems like a waste of effort to me.
prev parent reply other threads:[~2018-03-07 15:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1519433546-33879-1-git-send-email-pbonzini@redhat.com>
2018-02-26 22:13 ` [PATCH] KVM: VMX: expose the host's ARCH_CAPABILITIES MSR to userspace Konrad Rzeszutek Wilk
2018-02-26 22:23 ` Konrad Rzeszutek Wilk
2018-03-01 21:39 ` Radim Krčmář
2018-03-02 9:36 ` Paolo Bonzini
2018-03-02 21:42 ` Radim Krčmář
2018-03-07 11:53 ` Paolo Bonzini
2018-03-07 14:56 ` Radim Krčmář
2018-03-07 15:10 ` Paolo Bonzini
2018-03-07 15:39 ` Radim Krčmář [this message]
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